1. Field of the Invention
The present invention relates to a direct-ink-feed ballpoint writing implement using a low-viscosity ink, such as a water-base ink.
2. Description of the Related Art
Conventional ballpoint writing implements using a low-viscosity ink are classified into those of an impregnated wick type and those of direct-feed type. The ballpoint writing implement of an impregnated wick type has a barrel packed with an ink-holding wick of fibers impregnated with ink, and an ink-feeder wick for carrying the ink to a ball held in the tip of the barrel. A direct-feed ballpoint writing implement, which is relevant to the present invention, has a barrel having an ink tank containing ink, and a ball held in the tip of the barrel. In the direct-feed ballpoint writing implement, the ink is fed from the ink tank to the ball at a regulated rate.
A direct-feed ballpoint writing implement shown in FIG. 1 includes a barrel 21, a grooved member 22 (core), an ink feed member 23, a barrel cap 24, a ball holder 25, and a ball 26. The ink feed member 23 is formed by bundling polyester fibers and is capable of carrying the ink to the ball 26. It is important to set the ink feed member 23 so that the front end of the ink feed member 23 is located as close as possible to the ball 26. If the front end of the ink feed member is excessively close to the ball 26, or is in contact with the ball 26, the ball 26 is pressed against a socket formed in the ball holder 25 and any clearance is not formed between the ball holder 25 and the ball 26. Consequently, the ink is unable to wet the ball 26, faint and scratchy lines are drawn and, in the worst case, the ballpoint pen is unable to draw any lines.
An ink feed mechanism capable of feeding the ink at a proper rate to the ball must be interposed between the ink contained in an ink tank and the ball. The ink feed mechanism must be capable of properly feeding the ink contained in the barrel to the ball, of letting air into the barrel according to the consumption of the ink and of preventing the flow of the ink at an excessive high rate to the ball due to the rise of the ambient temperature.
The ink is carried from the ink tank to the ball by capillarity. A quantity of air corresponding to that of the ink sucked by the ink feed member must be discharged from the ink feed member to make the capillarity of the ink feed member effective, and a quantity of air equal to that of the ink that flowed from the ink tank into the ink feed member must be sucked into the ink tank for smooth ink feed.
Since the material forming the ink feed member is comparatively soft, it is difficult to locate the ink feed member accurately in the barrel. The location of an ink feed member formed by molding a plastic material in the barrel is easier than that of the ink feed member formed by bundling the polyester fibers. However, the ink feed member formed by molding a plastic material is inferior to the ink feed member formed by bundling the polyester fibers in ink carrying capability and is unable to insure stable writing.
When the direct-feed ballpoint writing implement is held with the ball in contact with a sheet, the ink is transferred from the ball to the sheet and an ink spot is formed even if the ball does not roll. If the direct-feed ballpoint writing implement is used with its axis tilted greatly from the vertical, the tip of the barrel cap is always in frictional contact with the sheet and is abraded gradually and, eventually, the socket of the ball holder wears out and becomes unable to hold the ball, and the ball falls off.
Accordingly, it is an object of the present invention to provide a direct-feed ballpoint writing implement including a ball holder, a compression spring placed in the ball holder and having a back set end and an ink feed member connected to the back set end of the compression spring, and capable of ensuring uniform ink feed and stable writing.
Another object of the present invention is to provide a direct-feed ballpoint writing implement including an ink tank containing ink, a ball holder, a ball held in the ball holder and a spring pressing the ball toward the tip of the ball holder, and capable of preventing the leakage of the ink contained in the ink tank from its tip due to the sudden rise of the ambient temperature or the sudden pressure drop of the ambient pressure.
A third object of the present invention is to provide a direct-feed ballpoint writing implement including a barrel and a cap put on the barrel to prevent the evaporation of the ink, and capable of preventing the leakage of the ink due to the pumping effect (pressure reducing effect) of removing the cap from the barrel, and of preventing the suction of air due to the pumping effect (pressure increasing effect) of putting the cap on the barrel.
A fourth object of the present invention is to provide a direct-feed ballpoint writing implement including a ball, a ball holder holding the ball in a socket formed in its tip part, and a spring pressing the ball against the socket of the ball holder, and capable of preventing the falling of the ball off the ball holder due to the gradual wear of the tip of the barrel cap by frictional abrasion caused by the sheet and the eventual loss of ball-holding capability of the ball holder when the direct-feed ballpoint writing implement is used with its axis tilted greatly from the vertical.
According to one aspect of the present invention, a direct-feed ballpoint writing implement comprises a barrel internally provided with an ink tank, a grooved member placed in a front part of the barrel and provided with a groove for guiding air and ink, an ink feed member pressed in the grooved member, a barrel tip fixedly joined to a front end part of the grooved member, a ball holder inserted in the barrel tip and put on a front end part of the ink feed member; and a ball held in a front end part of the ball holder; wherein a compression spring is extended at least between the ink feed member and the ball in the ball holder.